Time taken by sunlight to pass through a window of thickness `4 mm` whose refraactive index is `(3)/(2),` is

Options

A. `2 xx 10^(-1) sec`
B. `2 xx 10^(8) sec`
C. `2 xx 10^(-11) sec`
D. `2 xx 10^(11) sec`

Answer

C

Explanation

`v_(m) = (v_(a))/(mu_(m)) = (3 xx 10^(8))/(1.5) = 2 xx 10^(8)m//s`
Thus, time `= ("distance")/("velocity") = (4 xx 10^(-3))/(2 xx 10^(8))`
`= 2 xx 10^(-11) sec`